Few things are more heartwarming than an animal/caretaker reunion video. Dry eyes don't stand a chance the moment the pet's curiosity turns into recognition and full-throttle hugs and kisses ensue. Numerous scientific studies have proven time and time again that animals remember their caregiver even years later. But do pets remember their own siblings and parents after long periods of separation? The answer is a very clear cut: Maybe for some species. Probably not for others.
So, let's break down pet by species.
As Cuteness previously reported, though it can't be proven, there's a good chance that dogs will recognize their litter mates. According to Steven R. Lindsay, author of the "Handbook of Applied Dog Behavior and Training," a dog can recognize his parents and siblings, so long as they are together during the critical socialization phase from 3-weeks-old to 16-weeks-old.
Another study conducted by the University of Padua's Paolo Mongillo determined that a dog could recognize his owner's face. It could be hypothesized that if a dog can recognize the face of another species, he'll be able to recognize faces of his own.
A final thing to consider is that a dog's sense of smell supersedes that of humans by 10,000 to 100,000, so perhaps this ability allows a dog to detect a littermate he has not seen in years. But overall, it seems the key component to "knowing they're related" is if the dog shared some memorable moments with his fur family.
The likelihood of pets knowing they're related drops significantly when it comes to cats. Or rather, cats that are related may recognize their scents as familiar, but likely won't see each other as "family" in the way we think of it.
John Bradshaw, a cat behavior expert at the U.K.'s University of Bristol, says "once (cats are) separated from their mother, kittens seem to lose their memory of her quite quickly and usually fail to recognize her if reunited."
National Geographic reports sibling cats will often fight when reunited. Research shows there is a reason for this grumpy behavior, while female can recognize their male relatives enough to avoid mating with them.
Much like cats, birds operate under the same "out of sight out of mind" philosophy. Most birds do not recognize their family members after their first year.
There are exceptions to this, specifically for social birds like cranes and crows. Canadian geese may even rejoin their parents and siblings during winter and on migration. On the other hand, or other feather, many birds join a different winter flock from its siblings and parents.
For those asking, "well then how do you explain imprinting?" Great question. First, imprinting is the process by which an animal learns what they are. Birds don't automatically know what they are when they hatch — they visually imprint on their parents during a critical period of development. After imprinting, they will identify with that species for life. Ducks are a great example of a species that imprints, but there is no evidence that they recognize their parents or family members after their first year.
According to new research, a mama goat can recall her babies' bleats at least a year after mother and kid are separated.
Elodie Briefer, a postdoctoral researcher at Queen Mary University of London, states that even a year after weaning "(Mama Goats) still react more to the calls of the kid from a previous year than to the calls of familiar kids born to other females."
This was concluded after the researchers recorded the calls of 5-week-old pygmy goats. Between 7 and 13 months after these babies weaned from their mothers, the researchers played the bleats back to the moms and recorded how long the mother goats looked toward the sound or bleated back. "They found that mama goats responded more strongly to their own babies' cries than to the recorded cries of babies of other mothers." It appears the memory held even though the mothers had mated again and moved on to new offspring by the time of the follow-up experiment. So, though there's no concrete evidence that goats know they're related, this study is a strong indication that they at least recognize each other.
At the end of the day, science and studies can only provide educated guesses on whether or not animals "know" they're related. This could be one of those things where you just have to trust your gut. If it seems like your pet remembers his/her family. You're probably right.